Chemical, rheological, and volatile profiling of microalgae Arthrospira, Isochrysis, Nannochloropsis, and Tetraselmis species

Johannes Magpusao; Indrawati Oey; Biniam Kebede; Johannes Magpusao; Indrawati Oey; Biniam Kebede

doi:10.48130/fia-0024-0007

Figures (4) Tables (3)

Figure 1.
Microscopic images of microalgal suspensions at 40 × magnification: (a) Arthrospira sp., (b) Isochrysis sp., (c) Nannochloropsis sp., and (d) Tetraselmis sp.
Figure 2.
Viscosity (Pa·s) and shear stress (Pa) vs shear rate (s⁻¹) of untreated microalgal suspensions of Arthrospira sp., Isochrysis sp., Nannochloropsis sp., and Tetraselmis sp. Data points are means based on three replicates. Lines represent the Herschel-Bulkley fit.
Figure 3.
PLS-DA biplots describe the variation among the selected microalgae. Differently shaped symbols represent the different microalgae: Arthrospira sp., Isochrysis sp., Nannochloropsis sp., and Tetraselmis sp. The dots represent components.
Figure 4.
Individual plots of some representative discriminant compounds show variation among A. platensis, Isochrysis sp., Nannochloropsis sp., and Tetraselmis sp. Values are mean ± standard error (n = 3).

Parameters	Arthrospira sp.	Isochrysis sp.	Nannochloropsis sp.	Tetraselmis sp.
Proximate composition
Crude lipid (%, DB)	15.60 ± 1.12^a	12.01 ± 0.24^b	17.62 ± 0.84^a	8.80 ± 0.22^c
Crude protein (%, DB)	57.92 ± 0.52^a	10.11 ± 0.12^d	25.44 ± 0.79^b	15.54 ± 0.49^c
Total ash (%, DB)	5.81 ± 0.02^d	38.55 ± 0.08^a	25.82 ± 0.15^c	33.50 ± 0.39^b
Carbohydrate (%, DB)	14.06 ± 0.40^c	18.75 ± 0.05^b	19.68 ± 0.04^b	25.42 ± 0.65^a
Pigments
Chlorophyll a (mg/g DM)	0.051 ± 0.003^b	0.070 ± 0.001^a	0.008 ± 0.001^c	0.046 ± 0.001^b

Carotenoids (mg/g DM)	0.023 ± 0.001^b	0.137 ± 0.003^a	0.005 ± 0.000^d	0.014 ± 0.000^c
Total phenolic content (mg GAE/100 g DM)	245.64 ± 7.92^a	242.80 ± 2.92^a	195.63 ± 8.55^c	221.50 ± 9.24^b
Particle size distribution
d (0.1) (µm)	5.65 ± 0.10	2.69 ± 0.02	1.40 ± 0.00	5.80 ± 0.06
d (0.5) (µm)	9.08 ± 0.13	4.21 ± 0.03	2.35 ± 0.01	8.82 ± 0.03
d (0.9) (µm)	14.48 ± 0.16	6.44 ± 0.08	4.27 ± 0.04	13.13 ± 0.05
Rheological properties
Consistency coefficient, K (Pa·sⁿ)	0.013 ± 0.000^b	0.020 ± 0.001^a	0.008 ± 0.000^c	0.004 ± 0.000^d
Flow behaviour index, n (−)	0.900 ± 0.002^a	0.774 ± 0.002^c	0.802 ± 0.006^b	0.907 ± 0.013^a
Yield stress, σ₀ (Pa)	0.003 ± 0.001^a	0.004 ± 0.002^a	0.002 ± 0.000^a	0.001 ± 0.000^a
Values are mean ± standard deviation from independent replicates (n = 3). Means with different superscripts in the same row indicate a significant difference (p < 0.05). % DB refers to % dry basis.

Table 1.

Chemical composition and physical properties of the microalgal biomass used in this study.

Fatty acids	Arthrospira sp.	Isochrysis sp.	Nannochloropsis sp.	Tetraselmis sp.
C12:0	ND	ND	ND	5.72 ± 0.48
C14:0	2.52 ± 0.42^b	12.18 ± 1.75^a	1.84 ± 0.33^b	2.22 ± 0.02^b
C14:1	ND	7.83 ± 1.18	ND	ND
C16:0	45.30 ± 0.95^a	9.86 ± 1.71^c	21.53 ± 0.16^b	22.37 ± 0.41^b
C16:1n7	3.34 ± 0.11^c	5.40 ± 0.36^b	26.87 ± 0.95^a	1.33 ± 0.15^d
C18:0	1.81 ± 0.80^b	ND	0.81 ± 0.42^b	15.44 ± 0.85^a
C18:1n9t	ND	ND	0.60 ± 0.01^b	1.86 ± 0.07^a
C18:1n9c	2.89 ± 0.18^b	10.16 ± 1.14^a	4.46 ± 0.03^b	10.21 ± 0.16^a
C18:2n6c	22.58 ± 1.08a	6.03 ± 0.42^b	4.01 ± 0.04^c	7.38 ± 0.24^b
C18:3n3	ND	5.20 ± 0.17^b	ND	12.71 ± 0.41^a
C18:3n6	19.61 ± 0.46^a	ND	0.99 ± 0.01^c	2.39 ± 0.10^b
C20:0	ND	25.01 ± 2.97^a	ND	8.47 ± 0.26^b
C20:3n3	ND	ND	ND	ND
C20:4n6	ND	ND	4.48 ± 0.12^a	1.39 ± 0.13^b
C20:5n3	ND	ND	32.76 ± 0.10^a	5.59 ± 0.11^b
C22:6n3	ND	15.99 ± 1.57	ND	ND
Total SFA	49.63 ± 1.14^b	47.67 ± 0.96^b	24.18 ± 0.58^c	53.47 ± 00.09^a
Total MUFA	6.23 ± 0.05^d	23.73 ± 2.76^b	32.14 ± 0.84^a	16.52 ± 0.53^c
Total PUFA	42.20 ± 1.25^a	27.61 ± 1.17^b	42.34 ± 0.10^a	29.00 ± 0.26^b
Values are expressed as mean ± standard deviation (n = 3). Means with a different superscript in the same row indicate a significant difference (p < 0.05). ND means not detected.

Table 2.

The selected microalgae's relative fatty acid abundance as fatty acid methyl esters (FAME) by gas chromatography coupled with a flame ionisation detector (GC-FID).

VID	Identity	RI calculated	RI reference	Chemical class	VID	Identity	RI calculated	RI reference	Chemical class
Arthrospira sp.					0.982	2-Nonanone	1381	1390	Ketone
0.996	3-Ethyl-2,5-dimethylpyrazine	1438	1443	Pyrazine	0.98	(Z)-2-Pentenol	1304	1318	Alcohol
0.996	Safranal	1650	1616	Aldehyde	0.976	1-Penten-3-one	1016	1019	Ketone
0.995	1-Decene	1032	1050	Hydrocarbon	0.974	C16:1n7 (Palmitoleic acid)
0.994	1R-α-Pinene	1019	1013	Terpene	0.972	C20:5n3 (Eicosapentaenoic acid, EPA)
0.993	2,2,6-Trimethylcyclohexanone	1317	1319	Ketone	0.962	1-Heptanol	1440	1453	Alcohol
0.993	C18:3n6 (γ-Linolenic acid, GLA)				0.946	3-Octanone	1247	1253	Ketone
0.992	2-Butyl-2-octenal	1664	1656	Aldehyde	0.936	Benzyl alcohol	1867	1870	Alcohol
0.992	2,4-Dimethylbenzaldehyde	1737	1728	Aldehyde	0.888	3-Pentanone	973	980	Ketone
0.982	α-Cyclocitral	1442	1425	Terpene	0.885	1-Penten-3-ol	1147	1159	Alcohol
0.98	β-Cyclocitral	1626	1611	Terpene	0.832	2,7-Octadienol	1666	−	Alcohol
0.979	β-Ionone epoxide	1997	1962	Ketone	0.815	3-Ethyl-1,5-octadiene	1019	1015	Hydrocarbon
0.975	C18:2n6c (Linoleic acid)				0.812	(3E,5E)-3,5-Octadien-2-one	1566	1570	Ketone
0.97	trans-β-Ionone	1942	1940	Terpene	−0.838	Chlorophyll a
0.964	Protein				−0.839	Total phenolic content
0.957	Heptadecane	1690	1700	Hydrocarbon	Tetraselmis sp.
0.953	Heptanal	1177	1184	Aldehyde	0.976	C18:3n3 (α-Linolenic acid, ALA)
0.947	trans-2-Octenol	1598	1614	Alcohol	0.974	Dimethyl sulphide	743	754	Sulphur compound
0.942	C16:0 (Palmitic acid)				0.969	C12:0 (Lauric acid)
0.942	Nonanal	1387	1391	Aldehyde	0.957	2-Ethyl-3,5,6-trimethylpyrazine	1505	1506	Pyrazine
0.937	Pentadecane	1487	1500	Hydrocarbon	0.955	(Z)-4-Heptenal	1234	1240	Aldehyde
0.936	Hexadecane	1587	1600	Hydrocarbon	0.947	C18:0 (Stearic acid)
0.929	Geranyl acetone	1846	1859	Ketone	0.925	α-Ionone	1853	1840	Terpene
0.925	Octanal	1281	1289	Aldehyde	0.918	C18:1n9c (Oleic acid)
0.893	Isophorone	1404	1591	Ketone	0.894	Carbohydrates
0.887	1,2,4,4-Tetramethylcyclopentene	932	−	Hydrocarbon	0.857	Benzaldehyde	1526	1520	Aldehyde
0.869	2,2,4,6,6-Pentamethylheptane	944	949	Hydrocarbon	0.853	6-Methyl-5-hepten-2-one	1329	1338	Ketone
0.863	β-Pinene	1091	1112	Terpene	0.844	2,3-Butanedione	970	979	Ketone
0.858	D-Limonene	1187	−	Terpene	−0.87	Lipid
0.856	1-Nonanol	1643	1660	Alcohol	Isochrysis sp.
0.851	m-Xylene	1131	1143	Hydrocarbon	0.96	C22:6n3 (Docosahexaenoic acid, DHA)
0.851	α-Ionene	1697	1565	Hydrocarbon	0.96	C14:1 (Myristoleic acid)
0.843	1-Dodecene	1227	1243	Hydrocarbon	0.951	C20:0 (Arachidonic acid)
0.818	Hexyl acetate	1261	1272	Ester	0.948	Carotenoids
0.801	1-Octen-3-ol	1431	1450	Alcohol	0.936	3-Methyl-1,4-heptadiene	914	−	Hydrocarbon
−0.8	(3Z,5Z)-3,5-Octadiene	925	−	Hydrocarbon	0.933	C14:0 (Myristic acid)
−0.945	Ash				0.916	3-Methyl-2-(3,7,11-trimethyldodecyl) furan	2097	−	Furan
Nannochloropsis sp.					0.906	2,5-Dimethylbenzaldehyde	1746	1683	Aldehyde
0.991	2-Undecanone	1591	1598	Ketone	0.886	Maltol	1960	1969	Ketone
0.986	(E)-2-Pentenal	1125	1127	Aldehyde	0.865	(E,E)-2,4-Heptadienal	1460	1495	Aldehyde
0.985	1,3-Pentadiene	97	624	Hydrocarbon	0.835	2-pentylfuran	1221	1231	Furan
Retention indices (RI) for the individual volatile compounds were calculated and reference obtained from the National Institute Standards and Technology Standard Reference Database (National Institute of Standards and Technology n.d.). Individual fatty acids were identified by matching retention time with commercial standards.

Table 3.

Discriminant compounds and attributes selected per microalgal species based on the VID method confirmed with significant testing, listed in decreasing order of VID coefficient. Retention indices (RI) for the individual volatile compounds were calculated, and references were obtained from the National Institute Standards and Technology Standard Reference Database^[60]. Individual fatty acids were identified by matching retention time with commercial standards.